Hand tools that use leverage for acting upon a work piece are well known. Tools such as scissors, pliers, tin snips, and crimping tools function by varying the amount of pressure applied to a work piece by varying the amount of pressure applied by the user's hands to the tools. When a task requires an increase in force, more force must be correspondingly supplied by the user through an increase in muscular force applied to the tool.
Utilizing a hand tool generally requires a two-phase cycle. In the first phase, the tool is engages the work piece. In the second phase, the tool performs the desired task upon the work piece, such as gripping or spreading. The first phase requires comparatively less effort and more tool element movement or travel than the second working phase. Most common hand tools make no attempt to differentiate between the two phases of the cycle. During the working phase the operator increases the pressure. Slip-joint pliers are good examples of these types of tools.
Another class of tools uses the first type of applied force and a 3 bar mechanism to maximize pressure at the end of the stroke. Examples of this class are a locking action gripping tool such as the Vice-Grip.TM., or a cutting tool such as compound metal shears.
Still another class of tool use a ratcheting mechanism and an extra squeeze to trade travel for stored force. The Amp Crimper.TM., which uses 2-3 strokes to reach the desired pressure, is a good example of this type of tool.
A fourth class of tools is power tools, whether air or electric, which generally have so much force available that no attempt is made to control it.